I just installed the rear calipers and need to know if I should bleed first or set venting first. The pads are a pretty good distance from the rotor because the pistons are so far retracted. Also noticed my old pads didn't have the "anti-squeal" plate on the back but the new ones do. Are these worthwhile to use? The rear brakes were quiet with the old pads FWIW.

If the pistons are backed way out, it might not be wise to press the brake while bleeding. Set the venting clearance first, then bleed.

OK, is it necessary to reset the clearance after bleeding as well?

Eric Shea, the Pope of brakes, has a writeup on this. Do a search. He says to bleed FIRST then do the venting!!!!